A small featurless site, Brush Hill Sherborn

I described a site at the lower blue outline here. I also found rock piles at the upper blue outline, downhill and west of where the power lines cross Perry St. Here, along the edge of the swamp was a messy scatter of piled rocks. Sometimes they would separate and group up into what was an identifiable rock pile, then the mess continued - following along the edges of the wet area. Finally the piles got better formed and started to be evenly spaced and in lines. And then there were two parallel lines of evenly spaced piles forming a bit of a "grid". So it sort of became a marker pile site at one end.
This gives a good idea:

Nothing much to see. But I followed it along for a few paces thinking it was at least a deliberate construction of some kind:

What are we looking at here?

In the end, with piles like this:

It certainly qualifies as a "rock pile" site. And at this end, it is starting to show some inter-pile arrangement:

And some piles with outline structure:

We have seen things like this before. At Borderland State Park, at Birch Hill (NH), and in Acton. Pretty much everywhere. The last picture, with an outline and a larger rock to the side, is certainly familiar.
I have a "principle" which may be useful or not. It says:

The more widespread a pattern is the older it is. 

Accordingly, this is an old site for an observable reason and a theoretical one: it is decrepit and its patterns are widespread.